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23 June 2014

Law in Plain English: Greenhouse Gases Cases

This is one in a series of posts designed to describe court decisions in plain English. For more detail and background on the legal issues, see the link to the case below. For similar posts, click here.

Background: Following the Supreme Court's decision in Massachusetts v. EPA, 549 U.S. 497 (2007)—which clarified that greenhouse gases are an "air pollutant" subject to regulation under the Clean Air Act (CAA)—the Environmental Protection Agency (EPA) promulgated a series of greenhouse gas-related rules. Among them was the Tailpipe Rule, which set emission standards for cars and light trucks. Under the EPA's longstanding interpretation of the CAA, the Tailpipe Rule automatically triggered regulation of stationary greenhouse gas emitters. In other words, the EPA argued that once the Tailpipe Rule set motor-vehicle emission standards for greenhouse gases, the greenhouse gases became a regulated pollutant under the Act and thus subject to regulation by stationary emitters. Various states and industry groups challenged these rules, arguing that they are based on improper constructions of the CAA and are otherwise arbitrary and capricious. The DC Circuitdismissed and denied all petitions.

Issue: The question before the Court is whether EPA permissibly determined that its regulation of greenhouse gas emissions from new motor vehicles triggered permitting requirements under the Clean Air Act for stationary sources that emit greenhouse gases.

Holding: The Supreme Court ruled that the Act neither compels nor permits EPA to adopt an interpretation of the Act requiring a source to obtain a PSD or Title V permit on the sole basis of its potential greenhouse-gas emissions. EPA reasonably interpreted the Act to require sources that would need permits based on their emission of conventional pollutants to comply with BACT for greenhouse gases.